The present invention relates to “stack-lights”, a structure used to convey operating and warning information in industrial environments, and in particular to a stack light that provides for a sound module that can be placed between beacon modules in the stack.
Stack lights provide a short tower of different colored beacons that may be attached to, or in the proximity to, industrial equipment to provide a visual indication of equipment operating status to workers in the area. The tower promotes the visibility of the beacon lamps at different angles and locations while the different colors of the lamps as well as possible different flashing modes of lamps permit reliable communication of multiple types of information in a possibly noisy environment. In a typical installation, a simple stack light might have a red light indicating a machine failure or emergency, a yellow light indicating warnings such as over-temperature or over-pressure, and a green light confirming correct machine operation. Other combinations and colors are also possible.
Stack lights are typically constructed in a modular fashion, with multiple beacon modules “stacked”, the first one on a base unit and then each on top of the next. This modular construction allows the number, color, and order of the beacons to be flexibly selected by customer. Each beacon module includes a lamp (for example an incandescent or LED assembly) held within a transparent housing, for example a cylindrical colored tube, through which the lamp may be viewed. Upper and lower electrical connectors allow interconnection of the beacons to each other or a base to form the tower. Each beacon module also includes an internal electrical conductor system that communicates electrical signals from the bottom of the module to its top so that when the modules are assembled together, electrical continuity is established along the height of the tower between the base and the various modules without the need for separate wiring operations.
Typically each base provides a wire terminal block that may receive electrical wiring from an external switch source that controls the lighting of the beacons. Often that external switch source is an input/output (I/O) module associated with a programmable industrial control unit. Important status information developed during the execution of a control program on the industrial control unit may be relayed to the slack light for display.
In this regard, the stack light normally receives a power “common” together with multiple “signal lines” each which controls the power to a given beacon. The internal electrical connector system of the beacon modules communicates each signal line from the given beacon module to the next beacon module in a manner that shifts the signal wires so to connect a different signal wire to the lamps of each module depending solely on the order of the module in the stack.
It may be desired to add an audio alarm to the beacon modules of the stack light so as to consolidate warning systems in one location. For this purpose, a sound module may be constructed to be placed in the topmost position of the stack to receive electrical signal in the same manner as a beacon module but to energize an audio transducer rather than a lamp.